Oscillatory potentials in electroretinogram as an early marker of visual abnormalities in vitamin A deficiency

Vitamin A deficiency (VAD) caused by malnutrition and certain intestinal diseases induces visual impairments, including night blindness and photoreceptor cell dysfunction as indicated by reduced a- and b-waves in an electroretinogram (ERG). The effects of VAD on the inner retinal layer cells, including amacrine and ganglion cells, remain to be elucidated. The functions of these cells are reflected in oscillatory potentials (OPs), another component of the ERG. The present study investigated inner retinal layer cell function in VAD rats by analyzing OPs. In the present study, VAD was induced by feeding Brown Norway rats a vitamin A deficient diet for 10 weeks. A reduced body weight and peri-papillary opacification indicative of papilledema without histopathological alterations were observed, which are considered early symptoms of VAD. At this stage, the ERG revealed reduced OPs as well as a- and b-waves at various intensities of light stimulation. Further analysis indicated that the ratio of the alterations in OPs was more significant than those of a- and b-waves. After 5 weeks of recovery, these changes returned to control levels. These results suggest that OPs are the most sensitive and early marker of VAD-associated visual impairment in the ERG.